Direct smelting plant

ABSTRACT

A direct smelting plant for producing molten metal from a metalliferous feed material using a molten bath based direct smelting process is disclosed. The plant includes a gas delivery duct assembly extending from a gas supply location away from the vessel to deliver oxygen-containing gas to gas injection lances extending into a direct smelting vessel. The gas delivery duct assembly includes a single gas delivery main connected to the gas injection lances to supply oxygen-containing gas to the gas injection lances. The gas delivery main is located at a height above a lower half of the vessel.

TECHNICAL FIELD

The present invention relates to a direct smelting plant for producingmolten metal from a metalliferous feed material such as ores, partlyreduced ores and metal-containing waste streams.

A known direct smelting process, which relies principally on a moltenbath as a reaction medium, and is generally referred to as the HIsmeltprocess, is described in International Application PCT/AU96/00197 (WO96/31627) in the name of the applicant. The disclosure in theInternational application is incorporated herein by cross reference.

The HIsmelt process as described in the International application in thecontext of producing molten iron includes:

-   -   (a) forming a bath of molten iron and slag in a direct smelting        vessel;    -   (b) injecting into the bath: (i) a metalliferous feed material,        typically iron oxides; and (ii) a solid carbonaceous material,        typically coal, which acts as a reductant of the iron oxides and        a source of energy; and    -   (c) smelting metalliferous feed material to iron in the metal        layer.

The term “smelting” is herein understood to mean thermal processingwherein chemical reactions that reduce metal oxides take place toproduce molten metal.

The HIsmelt process also includes post-combusting reaction gases, suchas CO and H₂, released from the bath in the space above the bath withoxygen-containing gas and transferring the heat generated by thepost-combustion to the bath to contribute to the thermal energy requiredto smelt the metalliferous feed materials.

The HIsmelt process also includes forming a transition zone above thenominal quiescent surface of the bath in which there is a favourablemass of ascending and thereafter descending droplets or splashes orstreams of molten metal and/or slag which provide an effective medium totransfer to the bath the thermal energy generated by post-combustingreaction gases above the bath.

In the HIsmelt process the metalliferous feed material and solidcarbonaceous material are injected into the molten bath through a numberof lances/tuyeres which are inclined to the vertical so as to extenddownwardly and inwardly through the side wall of the direct smeltingvessel and into a lower region of the vessel so as to deliver at leastpart of the solid materials into the metal layer in the bottom of thevessel. To promote the post-combustion of reaction gases in the upperpart of the vessel, a blast of hot air, which may be oxygen-enriched, isinjected into an upper region of the vessel through a downwardlyextending hot air injection lance. Offgas resulting from thepost-combustion of reaction gases in the vessel is taken away from theupper part of the vessel through an offgas duct. The vessel includesrefractory-lined water cooled panels in the side wall and the roof ofthe vessel, and water is circulated continuously through the panels in acontinuous circuit.

The HIsmelt process enables large quantities of molten metal, such asmolten iron, to be produced by direct smelting in a single compactvessel. In order to achieve this it is necessary to transport largequantities of hot gas to and from the direct smelting vessel, transportlarge quantities of the metalliferous feed material, such asiron-containing feed materials, to the vessel, transport largequantities of the molten metal product and slag produced in the processaway from the vessel, and circulate large quantities of water throughthe water cooled panels—all within a relatively confined area. Thesefunctions must continue throughout a smelting operation—which desirablyextends over at least 12 months. It is also necessary to provide accessand handling facilities to enable access to the vessel and lifting ofequipment between smelting operations.

A commercial HIsmelt direct smelting plant based on a 6 m diametervessel (internal diameter of refractory hearth) has been constructed atKwinana, Western Australia. The plant is designed to operate the HIsmeltprocess and produce 800,000 tonnes per year of molten iron in thevessel.

The applicant has now carried out research and development work todesign a larger scale commercial HIsmelt direct smelting plant toproduce in excess of 1 million tonnes per year of molten iron via theHIsmelt process.

The applicant has been confronted with a number of problems in scalingup the HIsmelt process and has produced an alternate design for aHIsmelt direct smelting plant.

The present invention relates to a direct smelting plant that is analternative design for the commercial HIsmelt direct smelting plantmentioned above.

The direct smelting plant of the present invention can also be used tocarry out other direct smelting processes.

DISCLOSURE OF THE INVENTION

According to the present invention there is provided a direct smeltingplant for producing molten metal from a metalliferous feed materialusing a molten bath based direct smelting process that includes:

-   -   (a) a fixed direct smelting vessel to hold a molten bath of        metal and slag and a gas space above the bath, the vessel        including a hearth and a side wall;    -   (b) a solids feed assembly to supply solid feed material,        including metalliferous feed material and carbonaceous material,        from a solid feed material supply location away from the vessel        into the vessel;    -   (c) an oxygen-containing gas feed assembly to supply an        oxygen-containing gas from an oxygen-containing gas supply        location away from the vessel into the vessel, the        oxygen-containing gas feed assembly including (i) a gas        injection assembly including a plurality of gas injection lances        to inject the oxygen-containing gas into the vessel that extend        through openings in the vessel and (ii) a gas delivery duct        assembly extending from a gas supply location away from the        vessel to deliver the oxygen-containing gas to the gas injection        assembly, the gas delivery duct assembly including a single gas        delivery main connected to the gas injection lances to supply        the oxygen-containing gas from the gas supply location to the        gas injection lances, and the gas delivery main being located at        a height above a lower half of the vessel;    -   (d) an offgas duct assembly to facilitate flow of offgas from        the vessel;    -   (e) a metal tapping assembly to tap molten metal from the bath        during a smelting operation; and    -   (f) a slag tapping assembly to tap slag from the bath during a        smelting operation.

Preferably the gas delivery main is located above a connection of thegas injection assembly to the vessel.

Preferably the gas delivery main is a ring main that defines an endlesspath for gas flow within the main.

Preferably the gas delivery main is a horseshoe main.

Preferably the gas delivery main includes a single inlet foroxygen-containing gas and a plurality of outlets for oxygen-containinggas, with the number of outlets corresponding to the number of gasinjection lances.

Preferably the outlets for the oxygen containing gas are equally-spacedaround the vessel.

Preferably the gas injection lances can be disconnected from the gasdelivery duct assembly and removed from the vessel and replaced withreplacement lances.

Preferably the gas delivery duct assembly includes a plurality ofmembers that connect the gas delivery main to the gas injection lances.

Preferably the members are coaxial with the gas injection lances.

Preferably each connection member includes a spool that extends from aninlet end of one gas injection lance and an expansion joint that isconnected at one end to the spool and at the other end to one of theoutlets of the gas delivery main.

Preferably the oxygen-containing gas is air or oxygen-enriched air.

Preferably the gas injection lances extend downwardly and inwardlyrelative to the gas delivery main.

Preferably the gas delivery main is spaced away from the vessel so thatthere is a clearance between the vessel and the gas delivery main thatmakes it possible to remove the gas injection lances through theclearance.

Preferably the side wall of the vessel includes:

-   -   (a) a lower cylindrical section,    -   (b) an upper cylindrical section that has a smaller diameter        than the lower section, and    -   (c) a transition section that interconnects the upper and lower        sections.

Preferably the transition section includes the openings for the gasinjection lances and the lances extend through the openings into thevessel.

Preferably the transition section is frusto-conical.

Preferably the gas delivery main is located above the lower cylindricalsection of the vessel.

More preferably the gas delivery main is located above the uppercylindrical section of the vessel.

It is preferred particularly that the gas delivery main is locatedadjacent an upper part of the upper cylindrical section of the vessel.

In one embodiment, the gas delivery main is positioned to be outboard ofthe diameter of the lower cylindrical section of the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in more detail hereinafter by way ofexample with reference to the accompanying drawings, of which:

FIGS. 1 and 2 are perspective views from two different directions whichillustrates a direct smelting vessel and a part of an off-gas ductsystem that forms part of one embodiment of a direct smelting plant inaccordance with the present invention;

FIG. 3 is a perspective view of the vessel;

FIG. 4 is side elevation of the vessel;

FIG. 5 is a side elevation of the vessel which illustrates the layout ofrefractory bricks in the interior of the vessel;

FIG. 6 is a side elevation of the vessel which illustrates thearrangement of solids injection lances and the hot air injection lancesof the vessel;

FIG. 7 is a cross-section along the line A-A in FIG. 6;

FIG. 8 is a cross-section along the line B-B in FIG. 6;

FIG. 9 is a diagram that illustrates the arrangement of solids injectionlances in the vessel;

FIG. 10 is a diagrammatic top plan view of selected components of thevessel that illustrates extraction and insertion envelopes for thesolids injection lances and the hot air injection lances from thevessel;

FIG. 11 is a top plan view of the vessel; and

FIG. 12 is a top plan view of the vessel with the off-gas duct and thehot air blast delivery system removed.

DETAILED DESCRIPTION OF THE EMBODIMENT

The direct smelting plant shown in the Figures is suitable particularlyfor smelting metalliferous material in accordance with the HIsmeltprocess as described in International patent application PCT/AU96/00197(WO 96/00197).

The plant is not confined to smelting metalliferous material inaccordance with the HIsmelt process.

The following description is in the context of smelting iron ore finesto produce molten iron in accordance with the HIsmelt process.

The present invention is not confined to the production of molten ironand extends to direct smelting any metalliferous material.

The following description focuses on a direct smelting vessel of thedirect smelting plant and apparatus, such as solids and gas injectionlances, that are directly associated with the vessel.

The direct smelting plant also includes other apparatus, includingapparatus for processing feed materials for the vessel upstream of thevessel and apparatus for processing products (molten metal, molten slag,and offgas) produced in the vessel. Such other apparatus is notdescribed herein in detail because it is not the focus of the presentinvention but it nevertheless forms part of the plant. Such otherapparatus is described in other patent applications and patents in thename of the applicant and the disclosure in these patent applicationsand patents is incorporated herein by cross-reference.

With reference to the Figures, in the context of the present invention,the main features of the embodiment of the direct smelting plant shownin the Figures are:

-   -   (a) a fixed direct smelting vessel 3 to contain a molten bath 41        of metal and slag and a gas space 43 above the bath;    -   (b) a solid feed assembly that includes 12 solids injection        lances 5 a, 5 b to supply solid feed material, including        metalliferous feed material and carbonaceous material, into the        vessel;    -   (c) an oxygen-containing gas feed assembly to supply an        oxygen-containing gas to the vessel which includes:        -   (c)(i) a gas injection assembly in the form of 4 gas            injection lances 7 to inject the oxygen-containing gas into            the gas space and/or the bath in the vessel; and        -   (c)(ii) a gas delivery duct assembly that includes a ring            main 9 and a plurality of members 49, one associated with            each gas injection lance 7, that connect the ring main 9 and            the gas injection lances 7 to deliver the oxygen-containing            gas, typically air or oxygen-enriched air, to the gas            injection lances 7; and    -   (d) an offgas duct assembly that includes two offgas ducts 11 to        facilitate flow of offgas from the vessel away from the vessel;

With reference to FIGS. 1, 2, and 10, it is relevant to note at thispoint that the direct smelting plant also includes a superstructure 89formed from steel beams assembled together to define an octagonal-shapedouter perimeter 91, an octagonal-shaped inner perimeter 93 and a seriesof cross-members 95 interconnecting the perimeter beams. Thesuperstructure 89 supports the ring main 9 of the gas delivery ductassembly via hangers (not shown). The superstructure also includes aplurality of platforms (not shown) that provide workman access to thevessel 3 at different heights of the vessel 3.

The vessel 3 includes (a) a hearth that includes a base 21 and sides 23formed from refractory bricks, (b) a side wall 25 that extends upwardlyfrom the hearth, and (c) a torispherical roof 27. In order to place thesize of the vessel 3 into context, a vessel 3 that is designed toproduce 2 million tones per year of molten iron requires a hearthdiameter (internal) of around 8 m.

The side wall 25 of the vessel 3 is formed so that the vessel includes(a) a lower cylindrical section 29, (b) an upper cylindrical section 31that has a smaller diameter than the lower section 29, and (c) afrusto-conical section 33 that interconnects the two sections 29, 31.

It is evident from the following description and the drawings that the 3sections 29, 31, 33 of the side wall 25 of the vessel divide the sidewall 25 into 3 separate zones. The lower section 29 supports the solidsinjection lances 5 a, 5 b. The frusto-conical section 33 supports thegas injection lances 7. Finally, the upper section 33 in effect, is anoffgas chamber from which offgas leaves the vessel.

The side wall 25 and the roof 27 of the vessel 3 support a plurality ofwater-cooled panels (not shown) and the plant includes a cooling watercircuit. With reference to FIG. 5, the upper section 33 includes singlesteel panels and the lower section 29 includes double steel panels. Thecooling water circuit supplies water to and removes heated water fromthe water-cooled panels and thereafter extracts heat from the heatedwater before returning the water to the water-cooled panels.

The frusto-conical section 33 of the side wall 25 of the vessel 3includes openings 35 for the gas injection lances 7. The lances 7 extendthrough the openings 35. The lance openings 35 include mounting flanges37, and the lances 7 are mounted on and supported by the flanges 37. Thelance openings 35 are at the same height of the vessel 3 and arepositioned at equi-spaced intervals around the perimeter of the sidewall 25 of the vessel 3.

With reference to FIG. 5, in use of the vessel 3 to smelt iron ore finesto produce molten iron in accordance with the HIsmelt process, thevessel 3 contains a molten bath 41 of iron and slag which includes alayer (not shown) of molten metal contained in the hearth of the vessel3 and a layer (not shown) of molten slag on the metal layer 22. Themolten bath 41 shown in FIG. 5 is under quiescent conditions—i.e. underconditions in which there is no solids and gas injection into the vessel3. Typically, when the HIsmelt process is operating in the vessel 3 toproduce 2 million tones per year of molten iron, the vessel 3 contains500 tonnes of molten iron and 700 tonnes of molten slag.

With reference to FIGS. 3 and 4, the vessel 3 also includes 2 accessdoors 45 in the side 23 of the hearth to allow access to the interior ofthe vessel 11 for re-lining or other maintenance work in the interior ofthe vessel.

The access doors 45 are in the form of steel plates that are welded tothe sides 23. When access to the interior of the vessel 3 is required,the plates are cut away from the side 23 of the hearth and replacementplates are welded in position after the work in the vessel 3 has beencompleted. The access doors 45 are at the same height of the vessel 3.The access doors 45 are spaced at least 90° apart around thecircumference of the vessel 3. This spacing makes it possible forrefractory wall demolition equipment to extend through the doors 45 intothe vessel and demolish a substantial part of the refractories of arefractory-lined side wall while the vessel is hot. In addition, theaccess doors 45 are sufficiently large, typically 2.5 m in diameter, toallow bob-cat or similar equipment access to the interior of the vessel3.

With reference to FIG. 3, the vessel 3 also includes a similar accessdoor 47 in the roof 27 of the vessel 3 to allow access to the interiorof the vessel 11 for re-lining or other maintenance work in the interiorof the vessel 3.

In use, the four gas injection lances 7 of the gas injection assemblyinject an oxygen-enriched hot air blast from a hot gas supply station(not shown) located some distance away from the reduction vessel 11. Thehot gas supply station includes a series of hot gas stoves (not shown)and an oxygen plant (not shown) to enable an oxygen-enriched air streamto be passed through the hot gas stoves and into a hot gas delivery duct51 (FIGS. 2 and 11) which is connected to the ring main 9.Alternatively, oxygen may be added to an air stream after the air streamhas been heated by the stoves.

The purpose of the gas injection lances 7 is to inject a sufficient flowrate of the oxygen-enriched hot air at a sufficient velocity so that thehot air penetrates a fountain, typically an annular fountain, of moltenmetal and slag that is projected upwardly within the vessel 3 as part ofthe HIsmelt process and the oxygen-enriched hot air combusts combustiblegas, such as carbon dioxide and hydrogen released from the bath, that isin the fountain. Combustion of the combustible gas produces heat that istransferred to the molten bath when the molten metal and slag moves backdownwardly into the bath.

The gas injection lances 7 are straight-forward injection lances interms of basic construction and do not include swirlers for impartingswirl to oxygen-enriched air flowing through the lances. As is indicatedabove, research work of the applicant found that gas injection lances 7operating without swirl could achieve comparable performance to lancesoperating with swirl.

The gas injection lances 7 extend downwardly through the frusto-conicalsection 33 of the side wall 25 of the vessel 3 into the upper region ofthe vessel 3. The lances 7 are equi-spaced around the frusto-conicalsection 33 and are at the same height. The lances 7 are positioned toextend downwardly and outwardly to inject hot air towards the lowersection 29 of the side wall 25. It is important to note that it isundesirable that oxygen-containing gas contact the side wall 25 of thevessel—high temperatures generated by combustion at the side wall areundesirable from the viewpoint of vessel life. Consequently, the lances7 are arranged so that tips 53 of the lances 7 are points on ahorizontal circle.

The above-described downward and outward injection of oxygen-containingoff-gas is also desirable from the viewpoint of avoiding combustion ofreaction gases, such as CO, in a central vertical core of the vessel,generally identified by the numeral 139, in FIG. 5, and resultant lossof the heat with offgas from the offgas ducts 11.

As can best be seen in FIG. 3, the ring main 9 of the gas delivery ductassembly is a circular duct that is positioned above the vessel 3. As isdescribed above, the ring main 9 is connected to the hot gas deliveryduct 51 and receives oxygen-enriched air from that duct 51.

The ring main 9 includes 4 outlets 65.

The connection members 49 of the gas delivery duct assembly connecttogether the ring main 9 and the gas injection lances 7.

The hot connection member 49 for each gas injection lance 7 includes aspool 61 that extends from an inlet end of the lance 7 and an expansionjoint 63 that is connected at one end to the spool 61 and at the otherend to an outlet 65 of the ring main 9.

In use, the gas injection lances 7 receive oxygen-enriched hot air flowvia the ring main 9 and the connection members 49 that connect thelances 7 to the ring main 9. The ring main 9 delivers the same flow rateof hot air to each lance 7.

With reference to FIGS. 6 and 8, the location of each gas injectionlance 7 within the vessel 3 can be established theoretically by:

-   -   (a) positioning the lance 7 vertically with the tip 53 of the        lance 7 in a required position—indicated by the circular icons        55 in FIGS. 6 and 8—and then,    -   (b) with the lance tip 53 fixed, pivoting the lance 35° in a        vertical plane that intersects the lance tip 53 and is        perpendicular to a radial plane that intersects the lance tip 35        and then,    -   (c) with the lance tip 53 fixed, rotating the lance 30°        outwardly towards the radial plane.

The gas injection lances 7 are arranged to be removable from the vessel3.

Specifically, each lance 7 can be extracted by detaching the spool 61and the expansion joint 63 of the associated connection member 49 fromeach lance 7 and the ring main 9, thereafter unbolting the lance 7 fromthe mounting flange 37 of the lance opening 35 in the frusto-conicalsection 33 of the side wall 25, and thereafter connecting the lance 7 toan overhead crane (not shown) and lifting the lance 7 upwardly from theopening 35.

Replacement lances 7 can be inserted into the vessel 3 by the reverseprocedure to that described in the preceding paragraph.

The 12 solids injection lances 5 a, 5 b of the solids feed assemblyextend downwardly and inwardly through openings (not shown) in the sidewall 25 of the lower section 29 of the side wall 25 of the vessel 3 andinto the slag layer (not shown) of the molten bath 41. The lances 5 a, 5b are arranged so that the tips of the lances are points of an imaginaryhorizontal circle. The side wall 25 includes mounting flanges 69 and thelances 5 a, 5 b are mounted onto and supported by the flanges 69.

With reference to FIGS. 7 and 9, the solids injection lances 5 a, 5 binclude (a) 8 lances 5 a to inject iron ore fines and fluxes into thevessel 3 and (b) 4 lances 5 b to inject solid carbonaceous material andfluxes into the vessel 3.

The solid materials are entrained in an oxygen-deficient carrier gas.All of the lances 5 a, 5 b are the same external diameter and arepositioned at the same height of the vessel 3. The lances 5 a, 5 b areequi-spaced around the circumference of the lower section 29 of the sidewall 25 and are arranged so that the iron ore injection lances 5 a arearranged in pairs and there is a coal injection lance 5 b separatingeach adjacent pair of iron ore injection lances 5 a. The pairing of theiron ore lances 5 a to inject hot iron ore into the vessel reducespiping access issues around the vessel.

In use, the iron ore injection lances 5 a receive hot iron ore fines andfluxes via a hot ore injection system and the coal injection lances 5 breceive coal and fluxes via a carbonaceous material injection systemduring a smelting operation.

With reference to FIG. 9, the hot ore injection system includes apre-heater (not shown) to heat the iron ore fines and a hot ore transfersystem that includes a series of main supply lines 73 and pairs ofbranch supply lines 75 for each pair of iron ore injection lances 5 aand a supply of carrier gas to transport the hot ore fines in the supplylines 71, 73 and to inject the hot ore fines into the vessel 3 at atemperature of the order of 680° C.

With reference to FIG. 9, the carbonaceous material/flux injectionsystem includes single supply line 77 for each coal injection lance 5 b.

The outer diameter of the coal supply lines 75 is less than, typically40-60% of, the outer diameter of the hot ore branch lines 75. While theinternal diameter of the lances 5 a, 5 b is preferably the same, theneed to insulate the hot ore supply lines 75 and the hot ore branchlines 77 significantly increases the outer diameter of the lances.Typically, the hot ore branch lines 75 have the same outer diameter in arange of 400-600 mm and the coal supply lines 77 have the same outerdiameter in a range of 100-300 mm. In one particular example, the hotore branch lines 75 have an outer diameter of 500 mm and the coal supplylines 77 have an outer diameter of 200 mm.

The solids injection lances 5 a, 5 b are arranged to be removable fromthe vessel 3.

Specifically, the solid feed assembly includes an assembly to supporteach solids injection lance 5 a, 5 b during removal of the lance fromthe vessel and insertion of a replacement lance into the vessel 3. Thesupport assembly for each lance 5 a, 5 b includes an elongate track (notshown) extending upwardly and outwardly from the side wall 25 of thevessel 3, a carriage (not shown) movable along the track, and a carriagedrive (not shown) operable to move the carriage along the track, withthe carriage being connectable to the lances 5 a, 5 b to enable thelance to be supported on the track and moved upwardly and downwardly byoperation of the carriage drive and thereby extracted from the vessel 3.The support assembly is described in International applicationsPCT/2005/001101 and PCT/AU2005/01103 in the name of the applicant andthe disclosure in the International applications is incorporated hereinby cross-reference.

As will be evident from the above description, the direct smelting plantaccommodates removal and replacement of 16 lances comprising the 4 gasinjection lances 7 and the 12 solids injection lances 5 a, 5 b. Thevessel 3 is a relatively compact vessel. This compactness of the vessel3 and the positions of the ring main 9 and the gas ducts 11 in relationto the vessel 3 places tight space constraints on the removal andreplacement of the lances 7, 5 a, 5 b.

With reference to FIG. 10, in order to facilitate removal andreplacement of the lances 7, 5 a, 5 b, the direct smelting plantincludes a plurality of vertically extending overhead crane access zones97 a, 97 b.

The access zones 97 a are outboard of the ring main 9 and inboard of theouter perimeter 91 of the superstructure 89. There are 12 access zones97 a in total, corresponding to the 12 solids injection lances 5 a, 5 b.The access zones 97 a enable removal and replacement of the solidsinjection lances 5 a, 5 b.

The access zones 97 b are inboard of the ring main 9. There are 4 accesszones 97 b in total, corresponding to the 4 gas injection lances 7. Theaccess zones 97 b enable removal and replacement of the gas injectionlances 7.

The pair of offgas ducts 11 of the offgas duct assembly allow offgasproduced in a HIsmelt process operating in the vessel 3 to flow from thevessel 3 for downstream processing before being released to theatmosphere.

As is indicated above, the HIsmelt process preferably operates with airor oxygen-enriched air and therefore generates a substantial volume ofoffgas and requires relatively large diameter offgas ducts 11.

The offgas ducts 11 extend from the upper section 31 of the side wall 25at an angle of 7° to the horizontal.

As can best be seen in FIGS. 11 and 12, the offgas ducts 11 describe aV-shape when viewed from above the vessel 3. The longitudinal axes X ofthe offgas ducts 11 describe an angle of 66.32°. The offgas ducts arepositioned so that the central axes X of the ducts 11 intersect eachother and a point 101 on a radial line L that extends from a centralvertical axis 105 of the vessel 3. In other words, the axes X of theoffgas ducts 11 are not radials from the central vertical axis 105 ofthe vessel 3.

With reference to FIGS. 1 and 2, the direct smelting plant includesseparate offgas hoods 107 connected to each offgas duct 11 to cooloffgas from the vessel 3. The offgas hoods 107 extend verticallyupwardly from the outlet ends of the offgas ducts 11. The offgas hoods107 cool offgas from the vessel 3 via heat exchange with water/steampassing through the hoods to a temperature of the order of 900-1100° C.

With further reference to FIGS. 1 and 2, the direct smelting plant alsoincludes separate offgas scrubbers 109 connected to each offgas hood 107to remove particulates from cooled offgas. Additionally, each offgashood 107 is connected to a flow control valve (not shown) that controlsthe flow of offgas from the vessel and through the offgas hood 107. Theflow control valves may be incorporated with the offgas scrubbers 109.

With further reference to FIGS. 1 and 2, the direct smelting plant alsoincludes a single offgas cooler 111 connected to both offgas scrubbers109. In use, the offgas cooler 111 receives scrubbed offgas streams fromboth of the offgas scrubbers 109 and cools the offgas to a temperatureof the order of 25-40° C.

In use, the cooled offgas from the offgas cooler 111 is processed asrequired, for example by being used as a fuel gas in stoves (not shown)or a waste heat boiler (not shown) to recover chemical energy form theoffgas, and thereafter released into the atmosphere as a clean offgas.

The direct smelting plant also includes a metal tapping assembly thatincludes a forehearth 13 to tap molten iron continuously from the vessel3. Hot metal produced during a smelting operation is discharged from thevessel 3 through the forehearth 13 and a hot metal launder (not shown)connected to the forehearth 13. The outlet end of the hot metal launderis positioned above a hot metal ladle station (not shown) to supplymolten metal downwardly to ladles located at the station.

The direct smelting plant also includes an end metal tapping assembly totap molten iron from the vessel 3 at the end of a smelting operation outof the lower part of the vessel 3 and to transport the molten iron awayfrom the vessel 3. The end metal tapping assembly includes a pluralityof metal end tap holes 15 in the vessel 3.

The direct smelting plant also includes a slag tapping assembly to tapmolten slag from the vessel 3 periodically from the lower part of thevessel and to transport the slag away from the vessel 3 during asmelting operation. The slag tapping assembly includes a plurality ofslag notches 17 in the vessel 3.

The direct smelting plant also includes a slag end tapping assembly todrain slag from the vessel 3 at the end of a smelting operation. Theslag end tapping assembly includes a plurality of slag tap holes 19 inthe vessel 3.

In a smelting operation in accordance with the HIsmelt process, iron orefines and a suitable carrier gas and coal and a suitable carrier gas areinjected into the molten bath through the lances 5 a, 5 b. The momentumof the solid materials and the carrier gases causes the solid materialsto penetrate the metal layer of the molten bath 41. The coal isdevolatilised and thereby produces gas in the metal layer. Carbonpartially dissolves in the metal and partially remains as solid carbon.

The iron ore fines are smelted to molten iron and the smelting reactiongenerates carbon monoxide. Molten iron is removed continuously from thevessel 3 via the forehearth 13.

Molten slag is removed periodically from the vessel 3 via the slagnotches 17.

The gases that are transported into the metal layer and generated bydevolatilisation and smelting reactions produce significant buoyancyuplift of molten metal, solid carbon and slag (drawn into the metallayer as a consequence of solid/gas/injection) from the metal layerwhich generates upward movement of splashes, droplets and streams ofmolten metal and slag, and these splashes, droplets and streams entrainslag as they move through the slag layer. The buoyancy uplift of moltenmetal, solid carbon and slag causes substantial agitation of the slaglayer, with the result that the slag layer expands in volume. Inaddition, the upward movement of splashes, droplets and streams ofmolten metal and slag—caused by buoyancy uplift of molten metal, solidcarbon and slag—extend into the space above the molten bath and formsthe above-described fountain.

Injection of the oxygen-containing gas into the fountain via the gasinjection lances 7 post-combusts reaction gases, such as carbon monoxideand hydrogen, in the vessel 3. Heat generated by the post combustion istransferred to the molten bath when molten material falls back into thebath.

Offgas resulting from the post-combustion of reaction gases in thevessel 3 is taken away from the vessel 3 through the offgas ducts 11.

Many modifications may be made to the embodiment of the presentinvention described above without departing from the spirit and scope ofthe invention.

By way of example, whilst the embodiment described above includes 2offgas ducts 11, the present invention is not limited to this number ofoffgas ducts 11 and extends to any suitable number of offgas ducts 11.

In addition, whilst the embodiment described above includes a ring main9 to deliver the oxygen-containing gas to the gas injection lances 7,the present invention is not limited to this arrangement and extends toany suitable gas delivery assembly.

In addition, whilst the embodiment described above includes 4 gasinjection lances 7, the present invention is not limited to number andthe arrangement of the lances 7 and extends to any suitable number andarrangement of the lances 7.

In addition, whilst the embodiment described above includes 12 solidsinjection lances 5 a, 5 b, with 8 lances 5 a being iron ore injectionlances arranged in pairs and the remaining 4 lances 5 b being coalinjection lances, the present invention is not limited to this numberand arrangement of the lances 5 a, 5 b.

In addition, whilst the embodiment described above includes a forehearh13 to tap molten iron continuously from the vessel 3, the presentinvention is not limited to the use of the forehearth and to continuoustapping of molten iron.

1. A direct smelting plant for producing molten metal from ametalliferous feed material using a molten bath based direct smeltingprocess that includes: (a) a fixed direct smelting vessel to hold amolten bath of metal and slag and a gas space above the bath, the vesselincluding a hearth and a side wall; (b) a solids feed assembly to supplysolid feed material, including metalliferous feed material andcarbonaceous material, from a solid feed material supply location awayfrom the vessel into the vessel; (c) an oxygen-containing gas feedassembly to supply an oxygen-containing gas from an oxygen-containinggas supply location away from the vessel into the vessel, theoxygen-containing gas feed assembly including (i) a gas injectionassembly including a plurality of gas injection lances to inject theoxygen-containing gas into the vessel that extend through openings inthe vessel and (ii) a gas delivery duct assembly extending from a gassupply location away from the vessel to deliver the oxygen-containinggas to the gas injection assembly, the gas delivery duct assemblyincluding a single gas delivery main connected to the gas injectionlances to supply the oxygen-containing gas from the gas supply locationto the gas injection lances, and the gas delivery main being located ata height above a lower half of the vessel; (d) an offgas duct assemblyto facilitate flow of offgas from the vessel; (e) a metal tappingassembly to tap molten metal from the bath during a smelting operation;and (f) a slag tapping assembly to tap slag from the bath during asmelting operation.
 2. The plant defined in claim 1 wherein the gasdelivery main is located above a connection of the gas injectionassembly to the vessel.
 3. The plant defined in claim 1 wherein the gasdelivery main is a ring main that defines an endless path for gas flowwithin the main.
 4. The plant defined in claim 1 wherein the gasdelivery main is a horseshoe main.
 5. The plant defined in claim 1wherein the gas delivery main includes a single inlet foroxygen-containing gas and a plurality of outlets for oxygen-containinggas, with the number of outlets corresponding to the number of gasinjection lances.
 6. The plant defined in claim 5 wherein the outletsfor the oxygen containing gas are equally-spaced around the vessel. 7.The plant defined in claim 1 wherein the gas injection lances can bedisconnected from the gas delivery duct assembly and removed from thevessel and replaced with replacement lances.
 8. The plant defined inclaim 1 wherein the gas delivery duct assembly includes a plurality ofmembers that connect the gas delivery main to the gas injection lances.9. The plant defined in claim 8 wherein the members are coaxial with thegas injection lances.
 10. The plant defined in claim 8 wherein eachconnection member includes a spool that extends from an inlet end of onegas injection lance and an expansion joint that is connected at one endto the spool and at the other end to one of the outlets of the gasdelivery main.
 11. The plant defined in claim 1 wherein theoxygen-containing gas is air or oxygen-enriched air.
 12. The plantdefined in claim 1 wherein the gas injection lances extend downwardlyand inwardly relative to the gas delivery main.
 13. The plant defined inclaim 1 wherein the gas delivery main is spaced away from the vessel sothat there is a clearance between the vessel and the gas delivery mainthat makes it possible to remove the gas injection lances through theclearance.
 14. The plant defined in claim 1 wherein the side wall of thevessel comprises: (a) a lower cylindrical section, (b) an uppercylindrical section that has a smaller diameter than the lower section,and (c) a transition section that interconnects the upper and lowersections.
 15. The plant defined in claim 14 wherein the transitionsection includes the openings for the gas injection lances and thelances extend through the openings into the vessel.
 16. The plantdefined in claim 15 wherein the transition section is frusto-conical.17. The plant defined in claim 14 wherein the gas delivery main islocated above the lower cylindrical section of the vessel.
 18. The plantdefined in claim 14 wherein the gas delivery main is located above theupper cylindrical section of the vessel.
 19. The plant defined in claim14 wherein the gas delivery main is located adjacent an upper part ofthe upper cylindrical section of the vessel.
 20. The plant defined inclaim 19 wherein the gas delivery main is positioned to be outboard ofthe diameter of the lower cylindrical section of the vessel.